The invention relates generally to the field of magneto-rheological (MR) and electro-rheological (ER) substances, specifically methods for impregnating materials with MR and ER substances.
ER and MR fluids and powders are substances that rely on a magnetic to capable media compounded in a way that allows the substance to change form from a liquid or powder state to a rigid, solid state. These materials comprise micron-sized, magnetizable particles called fines, suspended in oil or other media. ER and MR powders consist solely of unsuspended magnetizable particles.
ER and MR fluids are similar in their operation. The main difference is that ER fluids are responsive to an electric field and MR fluids are reactive to a magnetic field. However, MR fluids do have some advantages over ER fluids.
In their liquid form, ER and MR fluids have a viscosity and consistency much like common motor oil. However, when an electric charge or magnetic field is applied, the fluids change form, becoming rigid and able to bond surfaces together. This rigid bonding mechanism results from a dipole moment introduced on the magnetic particles in the fluid from the electric charge or magnetic field. The particles form chains, aligning parallel to the electric charge or magnetic field. The strength of the bonding mechanism depends on the strength of the charge or field applied to the fluid and the size of the particles. The change in viscosity of the fluid takes place in a few milliseconds. ER and MR powders operate in the same manner, changing from a powder to a rigid form. MR fluids typically exhibit much stronger yield strengths than do ER fluids. MR fluids are also more resistant to temperature changes and have a high tolerance to impurities such as water. MR fluids can also be activated using a much lower voltage power supply. ER fluids require high voltage (near 5,000 volts) to operate. For purposes of the present disclosure, discussion herein of the terms xe2x80x9cER and/or MR fluidsxe2x80x9d is also meant to refer to equivalent ER or MR substances, such as powders.
It is desirable to impregnate powder metal parts, which have porous surfaces, with both ER and MR substances. This impregnation increases the efficiency of the ER and MR substances when they are used to bind the parts together in various mechanisms.
In one embodiment of the present invention, a method for impregnating a porous surface with a magneto-rheological substance includes the steps of providing a porous surface with a porosity sufficient to receive the magneto-rheological substance within the pores and covering a portion of one side of the porous surface with the magneto-rheological substance. The method further includes the step of providing a magnet on the opposite side of the porous surface to apply a magnetic field and draw the magneto-rheological substance into the porous surface.
In a second embodiment of the present invention, a method for impregnating a porous film with a magneto-rheological substance includes the steps of providing a porous film with a porosity sufficient to receive the magneto-rheological substance within the pores and immersing a portion of the film in the magneto-rheological substance. The method further includes the step of providing a magnet on a side of the porous film in order to provide a magnetic field to draw the magneto-rheological substance into the porous film.
In a third embodiment of the present invention, a method for impregnating a porous surface with an electro-rheological substance includes the steps of providing a porous surface with a porosity sufficient to receive the electro-rheological substance within the pores and covering a portion of one side of the porous surface with the electro-rheological substance. The method further includes the step of providing a magnet on the opposite side of the porous surface to apply a magnetic field and draw the electro-rheological substance into the porous surface.
In a fourth embodiment of the present invention, a method for impregnating a porous film with an electro-rheological substance includes the steps of providing a porous film with a porosity sufficient to receive the electro-rheological substance within the pores and immersing a portion of the film in the electro-rheological substance. The method further includes the step of providing a magnet on a side of the porous film in order to provide a magnetic field to draw the electro-rheological substance into the porous film.